The present invention relates generally to a three-dimensional x-ray imaging device. More particularly, this invention pertains to a mosaic crystal imaging device for three-dimensional acquisition and reconstruction of radiographic information with a stationary monochromatic x-ray beam, stationary object, and stationary detector. One important application of the invention is in improving the accuracy of mammography in the diagnosis of breast cancer.
The present invention was developed to overcome the deficiencies inherent in two-dimensional imaging of cancerous tumors and tissues. The present invention is directed towards the development of improved sensitivity and specificity in monochromatic x-ray imaging. Using standard x-ray techniques, the three-dimensional information characterizing an object is displayed as a planar two-dimensional image on the film or flat imaging plane. Using conventional imaging techniques, a small area of dense tumor would image the same as larger amounts of less dense normal tissue on standard films. To obtain a three-dimensional view of the target object using prior art methods, one would need to move the x-ray beam, the object, and/or the detector to gain the additional spatial information concerning the tissue, such as in CT or standard tomography. Because the x-ray beam cannot always be moved, the present apparatus and method was devised for x-ray beam rotation using mosaic crystals for stationary beam sources.
Prior art systems for x-ray imaging are shown in U.S. Pat. No. 3,772,522, issued to Hammond et al. on Nov. 13, 1993; U.S. Pat. No. 4,037,920, issued to Runciman et al. on Jul. 26, 1977; U.S. Pat. No. 4,118,099, issued to Weiss et al. on Oct. 3, 1978; U.S. Pat. No. 4,599,741, issued to Wittry on Jul. 8, 1986; U.S. Pat. No. 4,958,363, issued to Nelson et al. on Sep. 18, 1990; U.S. Pat. No. 5,262,951, issued to Flamholz et al. on Dec. 7, 1993; U.S. Pat. No. 5,509,043, issued to Van Der Sluis on Apr. 16, 1996; U.S. Pat. No. 5,628,314, issued to Kumagai on May 13, 1997; and U.S. Pat. No. 5,604,782, issued to Cash, Jr. on Feb. 18, 1997. Each of these patent disclosures is briefly outlined in the following discussion, and is hereby incorporated by reference.
U.S. Pat. No. 3,772,522, issued to Hammond et al. on Nov. 13, 1973, discloses a CRYSTAL MONOCHROMATOR AND METHOD OF FABRICATING A DIFFRACTION CRYSTAL EMPLOYED THEREIN. This specification teaches the use of a toroidal diffraction crystal with a curvature equal to the diameter of a Rowland circle. A monochromator is provided in which the diffraction crystal focuses x-radiation from a source at a point on the Rowland circle onto a target at a conjugate point on the Rowland circle.
U.S. Pat. No. 4,037,920, issued to Runciman et al. on Jul. 26, 1977, discloses a RADIATION SCANNING SYSTEM WITH TWO RELATIVELY MOVABLE REFLECTORS. This device teaches a radiation scanning system including two sets of planar reflective surfaces on which one set is movable relative to the other. A rotary assembly carrying one of the sets of planar reflective surfaces about an axis of rotation is also disclosed. A detector is arranged relative to an optical means such that the radiation enters the detector after sequential reflection from the reflective surfaces of the two sets.
U.S. Pat. No. 4,118,099, issued to Weiss et al. on Oct. 3, 1986, discloses IMAGE CODING AND DECODING USING COHERENT CODES. The disclosure teaches a laser, which may be monochromatic, split into two beams by semitransparent mirrors. The mirrors are shown at a common angle relative the source beam. The second mirror is at a spaced distance from the first mirror, wherein the spaced distance is in a direction perpendicular to the source beam. Additionally, the '099 patent teaches use of semitransparent reflective surfaces.
U.S. Pat. No. 4,599,741, issued to Wittry on Jul. 8, 1986, discloses a SYSTEM FOR LOCAL X-RAY EXCITATION BY MONOCHROMATIC X-RAYS. The patent teaches a system for x-ray fluorescence analysis which utilizes a plurality of parfocal diffractors to selectively monochromatize x-rays and focus them on a sample to be analyzed. Thus the '741 patent teaches use of rotating diffractive surfaces in conjunction with a stationary source and a stationary target. However, the diffractive surfaces are required to satisfy Johannson geometric conditions.
U.S. Pat. No. 4,958,363, issued to Nelson et al. on Sep. 18, 1990 discloses an APPARATUS FOR NARROW BANDWIDTH AND MULTIPLE ENERGY X-RAY IMAGING. The specification teaches a scanning system for dual energy imaging applications. The beam is scanned through a patient by means of adjusting the angle of incidence on a mirror.
U.S. Pat. No. 5,262,951, issued to Flamholz et al. on Dec. 7, 1993 discloses a X-RAY BEAM SCANNING METHOD FOR PRODUCING LOW DISTORTION OR CONSTANT DISTORTION IN X-RAY PROXIMITY PRINTING. The disclosure discusses a x-ray scanning method utilizing a pair of reflective mirrors to achieve a vertical scan (or a longitudinal scan through a patient). The mirrors may be moved linearly. The scan is used to etch a mask-wafer with low resultant distortion.
U.S. Pat. No. 5,509,043, issued to Van Der Sluis on Apr. 16, 1996 discloses an ASYMMETRICAL4-CRYSTAL MONOCHROMATOR. This device teaches a x-ray analysis apparatus comprising a dispersion system of crystals for monochromatizing an incoming beam. It also teaches a means for rotating crystal pairs about an axis perpendicular to the axis of the incoming beam.
U.S. Pat. No. 5,628,314, issued to Kumagai on May 13, 1997 discloses MULTI-LASER BEAM-SCANNING THROUGH LIVING BODY PENETRATION DIAGNOSIS AND TREATMENT APPARATUS. The invention is centered around a diagnostic apparatus to obtain a laser fluorescent image. The '314 patent discloses use of mirrors to scan the laser beam parallel to a stationary patient and rotation of the laser source and mirrors, in a semi-fixed relation, to obtain stereographic imaging. The source and mirrors are referred to as being in semifixed relation, rather than fixed relation, because the mirrors move to effect the parallel scan.
U.S. Pat. No. 5,604,782, issued to Cash, Jr. on Feb. 18, 1997 discloses SPERICAL MIRROR GRAZING INCIDENCE X-RAY OPTICS. The patent teaches an optical system for x-rays combining at least two spherical mirrors for each dimension in grazing incidence orientation. Of relevance is that the '782 patent teaches an apparatus for reflecting two beams of x-ray radiation at a focal plane. See FIG. 6 of the '782 patent disclosure. The '782 patent uses at least 6 spherical mirrors, 3 per beam, and means for orienting the mirrors such that the beams graze off the respective mirrors in a manner so as to reduce the comatic aberration of extremum rays. It teaches orienting the mirrors to direct the X and Y coordinates of the beam.
The teachings of the prior art are limited in their applications and embodiments. The prior art does not teach an axis of rotation for reflective surfaces where the axis of rotation is concentric with the axis of the incoming x-rays. Nor does the prior art teach the use of multiple opaque surfaces for splitting a monochromatic x-ray beam into two x-ray beams. Furthermore, the prior art fails to teach the use of non-Johannson diffractive surfaces with a stationary source and target with a concentric axis of rotation for the surfaces.
An additional feature not taught in the prior art is the three dimensional scan of a patient by converging a split beam onto the object that is to be imaged with a beam detector. Finally, the prior art fails to teach the use of a split beam in a linear and rotational mirror device as a means for obtaining a three-dimensional image of an object.
What is needed, then, is an imaging device for three-dimensional acquisition and reconstruction of radiographic information using a stationary monochromatic x-ray beam to view a stationary object with a stationary detector.